2-7
Chapter 2 Installation of this Device
(iv) Considering locations at which to attach to the sealed tank
When attaching the transmitter to a location that is higher than the lower flange of the sealed tank,
the following conditions must be satisfied. When considering locations, assume that the tank is empty.
Figure 2-4. Considering Sealed Tank Attachment Locations
P0: Tank internal pressure (absolute pressure: kPa abs)
ρ': Specific gravity of sealed liquid in capillary tube section
h: Height from tank lower flange to transmitter
If the transmitter is attached as in Figure 2-4, the pressure received by the diaphragm surface of the
lower flange of the transmitter body includes not only the internal pressure of the tank but also the
pressure of being pulled by the water head pressure of the sealed liquid in the capillary tube section.
For the pressure received by this diaphragm surface, any pressure not lower than the allowable
pressure low limit P (kPa abs) of the transmitter body is acceptable, but particular care must be
exercised in applications in which the internal pressure of the tank is at the vacuum level.
The attachment conditions are as follows.
P0 + (
- ρ' h
) ≥ P
102
h ≤
(P0 - P) × 102
ρ'
1 kPa = 102 mm H
2
O
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